1. Field of the Invention
This invention relates to refiners for particulate material and is more particularly concerned with paper pulp refiners equipped with resiliently flexible refining disks, and a method of refining.
2. Description of Prior Art
Conventional methods of refining paper stock, as it comes from beaters, digesters, or other pulping apparatus, generally involve passing the stock between rigid grinding or refining surfaces which break up the fibrous material and effect some further separation and physical modification of the fibers.
Substantial improvements in refiners for this purpose are disclosed in the copending application for patent of John B. Matthew and Edward C. Kirchner, Ser. No. 486,006 filed Apr. 18, 1983, assigned to the same assignee as the present application. According to that application, the rigidity constraints typically theretofore required in rotary disk refiners is overcome and substantial improvements in structure and operation are attained by the provision of resiliently flexible refining surface-supporting disks permitting operating pressure responsive adjustments of the relatively rotating refining surfaces axially relative to one another for attaining optimum material working results from the refining surfaces. More particularly, a rotor carries a plurality of the disks in axially spaced relation, and radially outer margins of the disks carry refining surface ring plates which confront and cooperate with complementary refining surfaces of a stator.
In order to maintain an orderly flow of stock to be refined through the disks, the disks have ports therethrough. In operation a large volume of paper making stock must flow through the ports. Due to mechanial strength requirements in the refining disk, these ports should be as small as possible. On the other hand, for refiner volume efficiency as great a velocity as practicable and thus flow force of paper making pulp stock must be maintained through the refiner. There may thus be a tendency toward pressure gradients through the refiner causing non-uniform refining, poor pulp development and therefore difficulty in maintaining proper web-forming control at the paper making machine in which the refined pulp is used. It is to the alleviation of such problems that the present invention is primarily directed.